The invention relates to a displacement machine for fluids, having a displacement chamber, arranged in the manner of a groove in a fixed casing, running approximately spirally from an inlet to an outlet and spanning more than 360.degree., into which chamber a likewise essentially spiral displacement body engages, which is held eccentrically drivably in such a way that each of its points executes a circular movement limited by the peripheral walls of the displacement chamber, the radii of curvature of the displacement body and the said peripheral walls being dimensioned such that, during its circulating, twist-free movement, the displacement body at least virtually touches the inner and outer peripheral walls at in each case a continuously progressing sealing line.
Such an embodiment can be taken for example from German Offenlegungsschrift No. 26 03 462. The constructions disclosed here require a particularly high expenditure on production in the pressure region, in other words where displacement chamber and displacement body have very small radii of curvature.
Comparable embodiments are to be taken for example from German Offenlegungsschrift No. 26 39 174, British Published Application No. 1 367 986, U.S. Pat. No. 4,558,997 and U.S. Pat. No. 4,627,800. All these embodiments share the disadvantage of a low overall efficiency.